Construction of punch dies

ABSTRACT

A punch die for punching depressions in a member for the separation by length of grain or the like, in which the punching face comprises a plurality of balls secured within a substantially common plane and in a fixed spaced relationship by being affixed to a backing plate.

O United States Patent 1151 3 638 474 Hannaford 1 1 Feb. 1, 1972 [54] CONSTRUCTION OF PUNCH DIES 2,456,682 12/ 1948 Dapprich ..72/75 [72] Inventor: Hedley G. Hannatord, 936 Port Road, 22:2? woodvme west South Australia 501 l,

AUSLLQUQ v .M FOREIGN PATENTS OR APPLICATIONS [22] Filed: Aug. 13, 1969 1,010,335 11/1965 Great Britain ..72/54 [211 App] No 849 750 79,528 12/1918 Switzerland ..72/349 Primary Examiner-Richard J. Herbst [52] US. Cl ..72/476, 76/107, 72/414 Attorney0ldham & Oldham [SI] Int. Cl ..B2ld 37/20 [58] Field of Search ..72/375, 376, 470, 75, 476, [57] ABSTRACT 72,478 414;.16/107; 100/295 A punch die for punching depressions in a member for the separation by length of grain or the like, in which the punching [56] References cued face comprises a plurality of balls secured within a substancommon plane and in a fixed Spaced relationship being afiixed to a backing plate. 921,739 5/1909 Rieske ..76/107 1,058,856 4 1913 Gibbs ..72/75 7 Claims, 5 Drawing Figures 2,075,286 3/1937 Jackes ..76/l07 cousrnucrrou F PUNCH DIES This invention relates to the manufacture of punch dies and a punch die so constructed, in particular a punch die for the purpose of punching a number of depressions or indents of accurately gauged size into a sheet of material, which is to be used for separation by length of grain or the like.

The problem to which this invention relates is the cost of such dies, in that, they are at present manufactured by normal die techniques and in achieving the accuracy required for the application stated, the cost of manufacture and therefore the cost of the completed dies is very high.

It is an object of this invention to propose improvements to the manufacture of such punch dies and also punch dies as such which while being able to maintain accurate location and gauging of the various critical portions, enables a substantial reduction of cost to be achieved.

A further object of the invention is to enable a die to have a portion of its punching face readily removable and replaceable if, for instance, due to a metal weakness a portion breaks down.

Accordingly, the invention can be said to reside in a punch die for the purpose described in which the punching face comprises a plurality of balls secured within a substantially common plane and in a fixed spaced relationship by being affixed to a backing plate.

The method of manufacture of a punch die according to this invention can be said to incorporate the steps of locating each of a plurality of balls with relation to a backing plate and securing this ball by suitable affixing means in this located position to the backing plate.

It is well known that the manufacture of steel balls as separate articles is a highly specialized art and because these can be made according to mass production techniques, their cost is very low while their accuracy and precision is very high for this cost. Because these can be very accurately located with respect to a support plate by using common engineering techniques rather than specialized die-making techniques, an extremely accurate punch die for the application above can be made by common fabrication techniques and, therefore, at a cost substantially less than previous methods of manufacture.

One important aspect of the invention is the ability by using common engineering techniques, such as either drilling or milling to achieve very accurately gauged apertures within a support plate. By locating the separately formed and therefore low-cost ball which can be precisely ground against the rim of an aperture cut by a precision tool ensure-3m accuracy of placement of the ball with relation to a support plate and therefore with relation to adjacent balls, insofar as the depth and width of the punching face formed by the ball is concerned, that can be considerably greater than would otherwise be obtainable with standard fabrication techniques. This enables the punch die to be constructed with very great accuracy by such fabrication techniques rather than by the otherwise specialized techniques of the punch die art in which the forms are cut out from an integral member.

The aperture which is cut in the support plate to locate the ball can be cut by either of several techniques, using however in each case a precision tool, so that the precision of the tool is imparted to the aperture and use of its form can be made in imparting accuracy to the ball location. In this context a circular aperture can be drilled through the support plate and the ball can be located by engaging the rim of this aperture, so that part of the ball extends to within the aperture, but most of the ball extends out past the face of the support plate. Securement of the ball in this location is preferably by a welding or brazing technique, the brazing being preferred in that, in the event of one of the balls cracking or breaking up after some usage, it can, independently of other balls in the die, be very readily dropped out by melting the silver solder support without detrimentally effecting the backing plate or any other ball, and a replacement ball can be quickly fitted in this location.

While at present I prefer brazing and therefore using silver solder, it is also possible to use resistance or arc welding or an adhesive material such as an epoxy resin if desired although as indicated I do not prefer these methods.

Rather than drilling a number of individual holes through a support plate, a slot or several slots can be milled either partly into or through the support plate, and again the edges of the milled slot can be used to provide an accurate location for the balls.

For my preferred application of this invention I will describe an embodiment with reference to drawings which are attached hereto and, in which:

FIG. 1 shows as a cross section the arrangement of a ball located by engaging the rim of an aperture in a support plate,

FIG. 2 shows this particular arrangement of FIG. 1 used for a number of adjacent balls and being located ready to apply a punching application to a sheet of metal,

FIG. 3 shows the closed position of the same arrangement of FIG. 2 particularly with the metal sheet having been pressed,

FIG; 4 is a face view of the supported balls, but particularly showing my preferred arrangement in which the support plate includes a number of open holes with two aligned rows of balls being used, and

FIG. 5 is a cross-sectional view of a jig by which the balls are held in position while being secured to their support plate.

Referring particularly to FIG. 1 the support plate 1 has a circular aperture 2 passing fully therethrough and a precisely formed steel ball 3 is located to have a portion within the aperture 2 by engagement against the rim 4 so that it extends substantially out past the face 5 of the support plate 1. v

The ball 3 is secured to the wall of the aperture 2 by silver solder, both the support plate and the ball being thoroughly heated and then particularly while the ball closes or plugs the end of the aperture 2 filling this with the silver solder 6.

FIGS. 2, 3 and 4 refer to the same embodiment and incorporate the arrangement of FIG. 1 in a practical assembly which is used for the purpose of punching a number of depressions or indents into a sheet of metal to be used for the separation by length of grain or the like.

Accordingly, the support plate 10 incorporating the plurality of adjacent balls 11 is used in conjunction with an anvil 12 which incorporates a number of correspondingly located apertures 13, each of which is a little larger than the corresponding ball 11 to allow for presence of the sheet of metal or the like there between and to allow for reasonable tolerance in the stretching of the metal or other material when being pressed out.

There is a small chamber 14 around this rim of each of the apertures 13, which assists in the metal member 15 as shown in FIG. 3 following a form which enables the depressions or indents to become or fit very close together.

The support plate 10 is backed by a backing plate 17 to reduce distortion when being used in the application.

In the application shown each of the balls 11 is secured accurately by engaging the rim of each of the apertures 18.

The accuracy of each ball and its placement ensures that the stretch of the metal is identical for each-indent and that therefore the diameter of each indent is substantially identical. This is an essential requireinent for the application for which the die is used.

A jig for manufacture of the die is shown in FIG. 5, the main feature of which includes the use of an underneath location plate 20 which is identical to the support plate 10, and in practice is drilled at the same time to ensure each of the apertures is identically located. The balls 11 are then placed on this plate 20 and the support plate 10 is then placed over the fitted balls 11 and a spacer 21 is positioned between the outer edges of the plates 10 and 20 the thickness of which is just slightly less than the free thickness between these plates. The plates 10 and 20 are then clamped down by clamps 23 on to the spacer 21.

Once clamped in this position the balls 11 are secured by heating the upper plate 10 together with the balls and when filling from the back each of the apertures 18 with silver solder.

The support plate as shown in FIG. 4 has additional apertures 25 the purpose for those being to enable a replacement row or rows of balls 11 to be secured thereto if those in position in the first rows should extensively fail.

The two rows of balls 11 in FIG. 4 are staggered for the obvious reason that this allows the greatest number of depressions or indents over a given area. The use of two rows thus staggered or multiples of two rows allows the use of simple manual indexing in a direction exactly transverse to the line of the rows. By making the anvil 12 extend past the punching station and including locating apertures it will be seen that on each punching action, the location of the succeeding sheet can be very accurately located by using the depressions formed and locating these in the locating aperture of the anvil.

This technique removes any need for an automatic stagger feed with a press which again results in a substantial cost sav- The term ball" used throughout this specification particularly includes and generally refers to precision ground and polished balls ground to a spherical shape to a very small tolerance. These are commonly used for ball bearings.

Balls not suitable for ball bearings however can obviously be used for the application of this invention and, in fact, it is preferable not to have a hardened face on the ball as this usually results in a greater breakage.

I claim:

1. A punch die for punching depressions in a member for the separation by length of grain or the like, in which the punching face comprises a planar backing plate having a plurality of cylindrical apertures extending therethrough defining rims on opposite sides of said backing plate, and a plurality of balls secured within a substantially common plane and in a fixed spaced relationship by each ball being fixedly secured to the backing plate and engaging a rim of a respective aperture so that a major portion of the ball extends from said plate.

2. A punch die as in claim 1 in which each ball is held in this location byadhering material extending between the ball and the walls of the aperture.

3. A punch die as inclaim l in which each ball is held in the located position by metal adhesion means afiixed in said apertures behind the balls.

4. A punch die as in claim 3 in which the metal providing the adherence between the backing plate and the ball has a melting temperature substantially lower than that of the material forming the backing plate or the ball.

5. A punch die for punching depressions in a member for the separation by length of grain or the like, as in claim 1, in which each ball has a diameter greater than the distanc across the aperture with which it is engaged.

6. A method of manufacture of a punch die for punching depressions in a member for the separation by length of grain or the like, the method including the steps of cutting a plurality of circular apertures through a planar backing plate thereby defining rims on opposite sides of said backing plate, locating a plurality of balls larger in diameter than the apertures within a substantially common plane and in a fixed spaced relationship by locatably engaging each ball against a rim of an aperture such that the aperture is plugged by the ball but the ball protrudes therefrom, and then affixing each ball in this posi tion by locating an adhesive material within the aperture to extend between the ball and the wall of the aperture.

7. A method as in claim 6 in which the adhesive material is silver solder. 

1. A punch die for punching depressions in a member for the separation by length of grain or the like, in which the punching face comprises a planar backing plate having a plurality of cylindrical apertures extending therethrough defining rims on opposite sides of said backing plate, and a plurality of balls secured within a substantially common plane and in a fixed spaced relationship by each ball being fixedly secured to the backing plate and engaging a rim of a respective aperture so that a major portion of the ball extends from said plate.
 2. A punch die as in claim 1 in which each ball is held in this location by adhering material extending between the ball and the walls of the aperture.
 3. A punch die as in claim 1 in which each ball is held in the located position by metal adhesion means affixed in said apertures behind the balls.
 4. A punch die as in claim 3 in which the metal providing the adherence between the backing plate and the ball has a melting temperature substantially lower than that of the material forming the backing plate or the ball.
 5. A punch die for punching depressions in a member for the separation by length of grain or the like, as in claim 1, in which each ball has a diameter greater than the distance across the aperture with which it is enGaged.
 6. A method of manufacture of a punch die for punching depressions in a member for the separation by length of grain or the like, the method including the steps of cutting a plurality of circular apertures through a planar backing plate thereby defining rims on opposite sides of said backing plate, locating a plurality of balls larger in diameter than the apertures within a substantially common plane and in a fixed spaced relationship by locatably engaging each ball against a rim of an aperture such that the aperture is plugged by the ball but the ball protrudes therefrom, and then affixing each ball in this position by locating an adhesive material within the aperture to extend between the ball and the wall of the aperture.
 7. A method as in claim 6 in which the adhesive material is silver solder. 